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AbstractHigh-resolution manometry using catheters with 36solid-state sensors spaced 1 cm apart has alreadybecome an established technique for esophagealmanometry where it has replaced water-perfused andstation pull-through manometry. Spatiotemporal plotswith color coding of pressure have greatly facilitatedthe analysis of esophageal peristalsis. Although suitablefor the length of the esophagus, the solid-statecatheter is insufficient for the study of longer segmentsof the gastrointestinal tract. A new technique withfiber-optic sensors has made it possible to constructcatheters with 72–144 sensors. Studies of colonicmotility have revealed that the most common motorpattern of the colon is a peristaltic contraction thattravels 7–10 cm in the retrograde direction. Earlierstudies using low-resolution manometry with7–45 cm between sensors led us to erroneous conclusionsregarding direction and frequency of contractionsand they largely missed both antegrade andretrograde contractions traveling short distances.Fiber-optic high-resolution manometry holds promisefor greatly improving our understanding of gutmotor physiology and hopefully also our understandingof patients with symptoms of disordered gutmotility.

This issue of Neurogastroenterology and Motilitycontains a remarkable report on the fundamentals ofhigh-resolution colonic manometry by Dinning et al.1The report is remarkable because it necessitates aparadigm shift in our views of colonic motor physiology.Using densely spaced fiber-optic sensors, theauthors convincingly show that our previous views ofcolonic motor activity were built on recordings thathad an inadequate spatial resolution of measurementpoints along the colon.

The previous conclusion that stationary contractionswere the predominant motor pattern of thecolon2 was erroneous, and so was the suggestion thatpropagation of pressure events was predominantlyantegrade.3 Instead, the most prevalent motor patternseems to be retrograde peristaltic sequences.1 Themajority of such contractions travel 7–10 cm and thisis probably the reason why they have largely remainedunnoticed by low-resolution manometry with pressuresensors spaced 7–45 cm apart.2–4 The only pattern thatwas correctly identified by low-resolution manometrywas the high-amplitude propagated contraction.

Clearly, high-resolution manometry will improveour understanding of colonic motor physiology but itremains to find out if this technique will also improveour understanding of patients with colonic symptoms.Our current techniques for investigating patients with,for example, constipation are indeed crude and limitedto measuring colonic transit and imaging of defecation.It will be interesting to apply the high-resolutiontechnique in patients with functional bowel disordersand those with underlying systemic disorders such asdiabetes mellitus, Parkinson disease, and multiplesclerosis. The high-resolution technique also holdspromise for aiding the development of targeted therapiesin colonic motility disorders.

Early experiments used water-perfusedmicro-catheters.5 The development of solid-state cathetersmade high-resolution manometry accessible for abroader audience.6 High-resolution manometry yieldslarge amounts of data but advances in computerperformance made it possible to display measurementsas spatiotemporal graphs with iso-contour plots andthis greatly facilitated analysis of data.7 The ease ofinterpretation has also led to application of the highresolutiontechnique for anorectal manometry.8

The main limitation with solid-state catheters is thenumber of sensors. Currently about 36 sensors spaced1 cm seems to be the limit. Solid-state technology mayadvance but the fiber-optic technique used by Dinninget al.1 has substantially increased the length of the gutsegment that can be studied with high-resolutionmanometry. For the first time, it may become possibleto study in detail also the small bowel. Pioneeringstudies in this part of the gut used water-perfusedcatheters and were limited to short segments of theduodenum but were able to demonstrate retroperistalsisduring late phase-III of the migrating motor complex.9,10 The clinical use of small bowel manometryhas been hampered by a total absence of standardization,few measurement points, usually two to eight,and comparatively long distances between sensors(3–15 cm).11–13 It would be of great interest to findout what we have missed while doing manometry ofthe small bowel in a way that only permits reliableestimates of migrating motor complexes.13The digestive functions of the colon mainly consistof bacterial fermentation of food residues. It isreasonable to assume that the motor activity of thecolon should be designed for optimizing fermentation,absorption of water, electrolytes and some nutrients,and packaging of waste. In the small intestine,digestion of food and absorption of nutrients are themain functions. We still know very little about therelation between meal composition and digestivemotor activity in the small intestine. Early experimentsin dogs indicated that different nutrients werealso handled differently.14 Fat, for example, seemed tobe associated with so-called clustered contractions, apattern that has been reported to occur more frequentlyin a number of disorders in humans15,16 butwhich can also be seen in healthy individuals.17Hypothetically, clustered contractions could representa specialized program aimed at facilitating micelleformation and digestion of fats. Whether such programsexist or not can now perhaps be studied usingfiber-optic high-resolution manometry of the smallintestine.

The report by Dinning et al.1 is a reminder to us all toavoid thinking that whatwecan measure is all there is tomeasure and things thatwecannot measure do not exist.We may think that intraluminal manometry onlymeasures the contractile activity of the circular musclelayer of the gut and that it tells us nothing about thelongitudinal muscle layer. It is true that the muscularactivity of the longitudinal muscle layer cannot easily beseen on intraluminal manometry. However, mathematicalmodeling of esophageal peristalsis with data frommanometry, radio-opaque marker studies and endosonographyindicates that contraction of longitudinalmuscle leads to local longitudinal shortening, which iscoordinated with contraction of circular muscle duringperistalsis.18 This means that the activity of the longitudinalmuscle layer is an integrated part of theperistaltic contraction and that intraluminal manometryreflects the activity of both muscle layers.

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